High efficiency mode-matched solid-state laser with transverse pumping

ABSTRACT

A high effieciency pumping scheme mode matches the TEMOO laser mode volume with a plurality of spaced apart laser diode pumping sources positioned along a lateral side of a block of laser material. The cavity resonator within the block is configured in tightly folded zig-zag configuration. Pump radiation from the diode pumping sources is collimated by an optical fiber and the fold angle is selected to mode match the pump radiation to the mode volume. Parasitic oscillation across the laser block are prevented.

RELATED APPLICATIONS

This application is a continuation of Ser. No. 103,557, filed Sept. 30,1987, which is a CIP of Ser. No. 035,530, filed Apr. 7, 1987, which is aCIP of Ser. No. 811,546 filed Dec. 19, 1985, now U.S. Pat. No.4,656,635, issued Apr. 7, 1987, which is a CIP of Ser. No. 730,002 filedMay 1, 1985, now U.S. Pat. No. 4,653,056, issued Mar. 24, 1987.

BACKGROUND OF THE INVENTION

The invention relates generally to resonator cavity designs forsolid-state lasers and more particularly to resonator cavity designs fordiode-pumped solid-state lasers.

Conventional optically-pumped solid-state lasers utilize broadband arclamps or flashlamps to laterally or transversely pump the solid-statelaser medium in a resonant cavity. The direction of pumping istransverse or orthogonal to the longitudinal axis of the resonantcavity. The entire medium is pumped so there is little correspondencebetween the pump volume and the TEMOO mode volume defined by the lasercavity; operation in TEMOO mode is desired. Much of the energy goes intoregions of the medium outside the volume occupied by the laser mode andtherefore does not contribute to amplification of the laser beam. Thuspumping efficiency is low (typically a few percent).

Laser diodes form efficient pumping sources; a variety of differenttypes of laser diodes, particularly laser diode arrays, e.g. SpectraDiode Labs Model No. 2410 GaAlAs laser diode array, in which a pluralityof emitters are phase locked together, and extended emitter laserdiodes, e.g. Sony Model Nos. SLD 301, 302, 303, 304 V/W, have been orcan be used. U.S. Pat. Nos. 4,653,056 and 4,656,635 and patentapplications Ser. Nos. 029,836 filed Mar. 24, 1987 and 035,530, filedApr. 7, 1987 describe a solid-state laser longitudinally end pumped by alaser diode source in which the pump volume is matched to the desiredTEMOO mode volume to optimize pumping efficiency. In the longitudinalend pump configuration, the direction of pumping coincides with thelongitudinal axis of the resonator cavity, and thus can be matched intothe laser mode volume. U.S. Pat. No. 4,665,529, issued May 12, 1987 andpatent application Ser. No. 048,717 filed May 12, 1987 describe asolid-state laser in which a laser diode source is coupled to a laserrod by means of an optical fiber to longitudinally end pump and modematch the laser. It is desirable to produce small size, low cost, highperformance solid-state lasers.

Thus the resonator/pump configuration is a key feature of laser designand performance. Lateral pumping schemes do not provide mode matchingand are therefore inefficient. End pumping schemes using laser diodesprovide mode matching and consequently high efficiency. However,previously-available laser diodes have often been limited in power,usually under 1W. Furthermore, even with higher power laser diodesources, the end pumped configuration limits the amount of energy thatcan be used, thereby limiting the power of the laser, since the powerdensities in the pump region of the gain medium become too high and theheat produced cannot be removed. Accordingly, it is desirable to providea resonator configuration which combines a transverse or lateral pumpgeometry with mode matching of the pump volume to the TEMOO mode volumesince lateral pumping allows more energy to be input into the mediumwhile mode matching uses the pump energy more effectively.

Another type of laser diode is a plurality of laser diode arraysfabricated into a multi-element bar structure. These laser diode arraybars typically have ten 1W laser diode arrays spaced along a 1 cm bar;each array has multiple emitters phase locked together. These array barsare not suitable for end pumping a solid-state laser but could be usefulfor transversely or laterally pumping a solid-state laser. However, ifthe bars are used as mere substitutes for arc lamps, little benefit willbe derived. Accordingly it is necessary to develop a laserresonator/pump configuration in which the output of the laser diodearray bar can be mode-matched to a desired mode volume (TEMOO) withinthe solid-state laser material.

SUMMARY OF THE INVENTION

Accordingly it is an object of the invention to provide a mode-matchedtransverse laser diode-pumped solid-state laser.

It is also an object of the invention to provide a mode-matchedsolid-state laser pumped by a laser diode array bar.

It is a further object of the invention to provide a solid-state laserresonator configuration which provides for efficient mode-matchedpumping by a multi-element laser diode pump source.

It is another object of the invention to provide a mode matched laserdiode pumped solid state laser which is pumped from a lateral side ofthe gain medium.

It is also an object of the invention to provide a solid-state laserwhich in which a plurality of laser diode pump sources spaced along alateral side of the gain medium are mode matched to the TEMOO mode.

The invention is a solid-state laser pumped by a plurality of discretelaser diode pump sources extending along a transverse or lateral face ofa block of laser material which are mode-matched to the resonator modevolume. Preferably, the pump source is a plurality of laser diode arrayswhich have been fabricated into a multi-element bar structure. Efficientoptical pumping of the solid-state lasers is accomplished by modematching the array output to the TEMOO mode within the solid-state lasermaterial in a tightly folded zig-zag cavity configuration. Byconfiguring the resonator in a tightly folded zig-zag between a pair oftransverse or lateral sides of the gain medium, the pump radiation canbe directed longitudinally into the mode volume, i.e., a transverselongitudinal pump scheme is achieved. Mode matching is accomplished bymatching the cavity mode volume to the divergence of the laser diodeemission. A cylindrical collimating lens, preferably a length of opticalfiber, is mounted parallel to and in a spaced relation with the diodebar by precision spacer means to substantially collimate the diodeemission in one direction (normal to the diode barlaser gain mediumjunction). The diameter of the fiber is chosen to match the pumpedregion to the size of the laser mode. In the other direction (in theresonator plane) the divergence of the laser diode emission (often a twolobe pattern) is matched to the fold angle of the zig-zag path of theTEMOO beam through the block of solid-state laser material.

BRIEF DESCRIPTION OF THE DRAWINGS:

In the accompanying drawings:

FIG. 1 is a top plan view of a transverse diode bar pumped mode-matchedsolid-state laser.

FIG. 2 is a top plan view of a mode-matched solid-state laser pumpedtransversely by a pair of laser diode bars.

FIGS. 3A-E are ray tracing diagrams of the collimation of a laser diodebar at various distances from a fiber optic collimator.

FIG. 4 is an end view of a laser diode bar with fiber optic collimator.

FIG. 5 is an end view of a fiber-optic collimated laser diode bar.

FIGS. 6 and 7 are perspective views of two embodiments of a fiber-opticcollimated laser diode bar.

FIG. 8 is a top plan view of a plurality of diode arrays matched to themode volume in a solid-state laser cavity having a tightly foldedzig-zag configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

The invention is a solid-state laser having a resonator/pump geometrywhich provides effective coupling of high average power laser diode barsto the solid-state laser active medium. The invention utilizes a lasercavity having a tightly folded zig-zag configuration within a block oflaser material so that a laser diode bar placed along a transverse orlateral face of the block of laser material can be mode-matched to theTEMOO mode volume. This solid-state laser oscillator optimizes theoverlap between the lasing TEMOO mode and the regions pumped by thediode bar, using optional simple collimating optics and the fold angleof the resonator cavity. By folding the resonator cavity, thelongitudinal axis of the resonator can be made substantially normal to atransverse or lateral side of a block of laser material, instead ofbeing parallel to the sides, so that the resonator cavity can be pumpedlongitudinally at a number of spaced intervals along the sides insteadof merely from an end.

A solid-state laser 10, and shown in FIG. 1, is formed with a block 12of Nd:YAG or other solid-state laser material. Laser cavity formingmeans, e.g., a mirror 14 which is highly reflective to the laserradiation and an output coupler mirror 16 which is partly transmissiveto the laser radiation are positioned around the block 12 to form alaser cavity which extends within the block 12. The mirrors 14, 16 areoriented at angles to block 12 so that the resonant cavity configurationwithin block 12 is a tightly folded zig-zag 18 at a preselected foldangle between a pair of opposed lateral sides 20, 22 of block 12. Asillustrated, mirrors 14, 16 are on the same side of block 12 but canalso be on opposite sides.

The surfaces of sides 20, 22 are coated with a suitable anti-reflection(AR) coating; further coating layers which form a high reflectively (HR)coating are placed on the portions of sides 20, 22 where the laser beamis to be reflected back into block 12. As shown, the region of side 20between the two entrance/exit points of the laser beam has an HRcoating, while all of side 22 could have an HR coating. The coatings arefurther described herein. Diode bar 24, placed along side 22, forms thepumping source. Diode bar 24 contains a plurality of separate laserdiode arrays 26 spaced along its length. The emissions from laser diodearrays 26 on bar 24 are matched to the mode volume of laser 10 by meansof a fiber lens collimator 28 and by selecting the fold angle of thezig-zag portion 18 of the resonator to match the divergence of diodearrays 26, as will be further explained below. An optional intra-cavityelement 34 may also be included, as described herein. In some cases,collimator 28 may be unnecessary; diode arrays 26 could be buttedagainst block 12.

A variation of the basic embodiment which uses a pair of diode bars topump the solid-state laser is shown in FIG. 2. A separate diode bar 24is placed along each side 20, 22 of block 12 of laser material to pumpthe zig-zag portion 18 of the resonator within block 12. Highlyreflective mirror 14 and output coupler 16 are on opposite sides ofblock 12 to form the resonant cavity and are oriented to produce thedesired fold angle. Each diode bar has a plurality of separate diodearrays 26 which are collimated by a fiber lens 28.

Many different embodiments of the basic elements are possible; one, two,three or more diode bars can be used, with the bars on one side or bothsides of the block of laser material. The cavity forming mirrors can beon the same or opposite sides of the block. Each fold in the resonatorcan be pumped by a laser diode array, or only every other fold, or everythird fold, etc.; the folds can be pumped from only one side or fromboth sides.

The great advantage of this resonator configuration is that the pumpvolume can be very closely matched to the mode volume in the resonator.The positions and shapes of mirrors 14, 16 will determine the modevolume within the resonator; TEMOO mode is highly desirable because ofits single lobe pattern. The resonator configuration allows a pluralityof discrete pumping sources, preferably separate diode arrays, spacedalong a multi element diode bar, to be placed along a lateral side or apair of opposed lateral sides so that a much greater portion of thelaser gain medium can be pumped, and to maximize the efficiency bymatching the pumping volume of all the diode arrays to the desired modevolume of the resonator. The result is a configuration of very highefficiency and very high gain.

A preferred embodiment of the laser diode bars has ten one-watt diodearrays located on a 1 cm piece of GaAs. The individual arrays are 200microns wide and are spaced 1 mm apart. These diode bars are preferredbecause (1) all the diode laser wavelengths on the bar will be closelymatched since they are manufactured on the same monolithic piece ofGaAs, (2) spacing the diodes 1 mm apart reduces thermal loading of thesubstrate, and (3) combining many diodes on a bar reduces packaging costand improves yields. However, different arrangements of diode bars canbe utilized, e.g., different number or spacing of the individual arrays.Alternatively, in place of a diode bar containing many discrete arrays,a plurality of separate individual diode arrays could be positionedalong the side of the block. The diode arrays often have a two lobepattern with a greater divergence in the direction normal to the planeof the bar; the divergence is typically about 7° full angle in the planeof the bar (lobe to lobe) or a numerical aperture (N.A.) of about 0.15,and 28° or 0.6 N.A. in the plane normal to the bar. Thus matching thepump beam to the mode volume in the direction normal to the plane of thebar is more difficult and requires some additional optics.

A preferred embodiment of a collimator means to collimate the output ofthe diode bar uses an optical fiber as a cylindrical lens. A typicalresonator configuration has a 200-300 micron wide beam; therefore a300-400 micron cylindrical lens would be suitable. Typical multimodeoptical fibers have this diameter and will form a good low costcollimator provided the fiber can be positioned in a manner that willcollimate all the individual spaced arrays. Thus although a fiber couldbe used to collimate a single array, it is necessary to provide a meansfor using a fiber to collimate the whole bar. FIGS. 3A-E show thecollimation of the output of a laser diode array 26 by an optical fiber28 into a solid-state laser block 12. The diode arrays 26 are spaced at1, 10, 20, 30 and 50 microns, respectively, from fiber 28 of about 250microns diameter. At 1, 10 and 50 microns spacing the beam is notsufficiently collimated. Thus, in order to use an optical fiber tocollimate the arrays on a diode bar, the fiber must be held at a spacingof 30±10 microns (i.e. about 20-40 microns) along the entire bar.

As shown in FIG. 4, an optical fiber 28 is mounted in a spacedrelationship with diode bar 24 so that the output from each laser diode26 is substantially collimated to a pump beam 30 which is incident intolateral side 22 of YAG block 12. Side 22 has a coating which is highlytransmissive to the pump radiation (typically about 800 nm) butreflective to the laser radiation. The diameter of fiber 28 is chosen toproduce a pump beam 30 with a diameter which substantially matches (isslightly smaller than) the diameter of the laser beam 32, thereby modematching the pump beam to the mode volume in one direction (normal tothe plane of the resonator). The fiber 28 is positioned relative to thediode bar 24 by means of a precision spacing means 29, e.g., a copperheat sink with steps, with diode array 26 at the focus so the radiationwill be collimated. Precision spacing means 29 maintains fiber 28 in aprecise parallel spaced relationship with bar 24 along its entire lengthto collimate the output of all the arrays 26 into a line of light.Typically the gap between the diode bar and fiber is about 20-40 micronsand the distance between the diode bar and YAG block is about 450microns. Although an optical fiber is not a perfect collimator becauseof spherical aberration which causes beam spread, the pump energy willbe absorbed in a relatively short distance within the laser medium (anabsorption length) so that the spread is negligible and the opticalfiber is a highly effective collimator when it is correctly positionedin the manner described. This collimated laser diode bar in itself isalso considered a part of the invention.

A preferred embodiment of a fiber optic collimated laser diode bar 31 isillustrated in FIG. 4. The spacing means 29 is formed of a multi-stepcopper or other heat sink 38. The diode bar 24 which contains arrays 26is mounted on one step 40 while the fiber 28 is mounted (e.g. epoxied)onto a lower step 42. Steps 40 and 42 are separated by an intermediatestep 44 against which the fiber 28 is positioned to maintain the correctfiber to diode working distance (about 30 microns) along the length ofbar 24 (about 1 cm). The fiber diameter is typically about 250-350microns, or other suitable multimode fiber diameter depending on themode volume, to collimate the arrays. A pair of embodiments of thecollimated laser diode bar of FIG. 5 are shown in FIGS. 6 and 7. In FIG.6 the steps 42, 44 for mounting the fiber 28 are formed along the entirelength of spacer 29 (heat sink 38) while in FIG. 7 the steps 42, 44 areformed only at the ends 46 of spacer 29. The diode arrays 26 are formedor mounted on step 40. Pump beams 30 from arrays 26 are collimated inone direction but still have two lobe divergence in the other. Analternate method of precision spacing the fiber from the diode bar is touse UV curing epoxy to space the fiber, and to apply the UV when thecollimation is acceptable. Any precision spacer or adjustment meanswhich can maintain end-to-end variation of ± 10 microns along the barlength (1 cm) can be used.

Once the pump beam is mode-matched in one direction, as previouslydescribed, it must also be matched in the other direction (in the planeof the resonator). As shown in FIG. 8, the individual diode arrays 26are separated by a distance d, preferably 1 mm, on diode bar 24. Pumpbeam 30 is collimated by fiber 28 in the direction normal to theresonator plane so the pump beam width in that direction is slightlysmaller than the width of the laser beam 32. In the plane of theresonator, the mode volume in the tightly folded portion 18 of theresonator is matched to the divergence of diode arrays 26. Frequently,the diode arrays produce a two lobe output so that one lobe goes intoeach portion of the V in the folded beam. The mode matching isaccomplished by controlling the fold angle A. The diameter of laser beam32 is typically about 300 microns. The resonator geometry and beam modevolume must be such that the beams in the folds do not overlap, so thatthe laser beam can exit the block of laser material at the edge of thehighly reflective coating on the block surface. The fold angle A is verysteep, typically 5°. The configuration is totally different from theconventional zig-zag slab laser in which the zig-zag is produced bytotal internal reflection (TIR) of the beam; in the present inventionthe fold angle is too steep for TIR. The laser diode beam may be singlelobe, e.g., as produced by the Sony extended emitter laser diodes.Accordingly it is desirable to produce a folded zig-zag configurationwhere the distance L at which the beam 32 does not overlap between the V(i.e. the two parts of the V totally separate) is equal to or greaterthan the absorption length of the pump beam radiation in the particularlaser medium. Therefore, the fold angle will depend on the diode arrayspacing and ability to remove the beam from the zig-zag portion of theresonator. The diodes need not pump every single fold, but may pumpevery other fold. The fold angle can be made very steep, particularly inthe case of a single lobe pump beam so that the pump beam direction mostclosely coincides with the longitudinal axis of the laser beam in theregion of the laser beam where the pump radiation is absorbed by thegain medium. The fold angle is adjusted, by means of the cavity formingmeans, to follow out the intensity distributions of the pump source withthe TEMOO mode and maximize overlap.

A number of different factors must be considered to design the cavity,as illustrated by the following preferred embodiment. First is the blockof laser material. A YAG bar 5 mm×5 mm×20 mm can be produced, machinedflat to half a wavelength over the whole length. Thus the length of thefolds (distance between the two lateral sides) will typically be about 5mm. Next is the laser beam mode volume. The radius of the cavity formingmirrors is typically 100 cm, and the mirrors are placed about 2 cm fromthe laser block. With ten folds (20 passes across the block) the totalcavity length is about 15 cm, and has a 1/e² beam diameter of about 300microns. A 300 micron beam is desirable because the diode arrays are 200microns and can be matched to the mode volume for maximum pumpingefficiency. However changing the cavity (mirror radius) can produceother beam sizes which may be suitable in other embodiments, e.g. if a0.5 cm diode bar is used with ten 0.5 W arrays of 100 micron diameter(also with a suitable narrower fiber collimator).

In order to remove the beam from the block, the beam must pass through aregion that is not reflecting (i.e. only AR coated) and skim by a regionthat is highly reflecting (HR coated). As a general rule, to avoidsignificant diffraction losses, the aperture must be about 3 times the1/e² beam diameter to avoid significant diffraction loses. Thus for aTEMOO beam diameter of 300 microns, the nearest edge must be about 500microns. As shown in FIG. 8, beam 32 exits side 20 at point 48. Thedistance between folds is about 1 mm. Thus point 50 which is directlyacross from the first diode array 26 is about 500 microns from exitpoint 48. Thus the HR coating should end sharply at point 50 so the beamcan exit without significant diffraction loss.

The coating method uses a precision mask to match the end to end lengthof the bar. The mask is very thin, e.g. 2 mils (0.002 in) for a sharpcutoff or steep edge so the beam can exit without significantdiffraction loss. The coatings are conventional optical coatings. Bothsides are first coated with a AR coating, e.g., two layers which alsoform the first two layers of the HR coating. Any side on which there areno exit points can be completely coated with a multi-layer (e.g. 20layer) HR coating. The central portion of the other sides is then coatedwith the HR layers using the mask.

A potential problem because of the high gain is the occurrence ofparasitic oscillation straight across the laser medium block from thediode array, i.e. between the zig-zag folds. One solution is to coat theblock surface in a series of HR stripes so the surface coating where thezig-zag folds contact the surface are highly reflective but the surfacedirectly across from the diode array is only AR coated to create awindow which will not produce resonance. The point 52 (and similarpoints at each fold), shown in FIG. 8, which is directly across from anarray 26 should not be HR but only AR coated. This could be produced byusing a coating mask which forms stripes of HR coating only where thebeam reflects and leaves gaps in the HR coating (i.e. only AR coating)at points 52 (the HR coating would also be moved slightly off point 50at the exit point). Alternatively, the entire surface beneath the maskcould be HR coated and then stripes of HR coating could be removed atpoints 52, e.g. by a laser. Another solution is to slightly wedge thenormally parallel opposed sides of one laser block; however, this mayrequire nonuniform spacing of the diodes to compensate.

The lasers according to the invention represent a major advance inability to effectively pump a solid-state laser using a high power diodebar pump source by mode matching to the desired TEMOO mode volume. Theselasers can be made extremely compact and have very high performancecharacteristics. Any of the wide variety of solid-state laser materialscan be used; in particular Nd: YAG and Nd:glass are two well-knownmaterials which have been extensively used for other applications. Ingeneral, the active medium should have high slope efficiency, broad pumpbands, and good thermal conductivity. A Nd: YAG laser has a very strongline at 1.06 microns and weaker lines at 0.946 and 1.3 microns, all inthe IR. For operation in the visible, a frequency doubler could be addedto the laser cavity, represented by intracavity element 34 in FIG. 1,producing 532 nm, 473 nm and 651 nm, respectively. Power levels of 10 Wat 1.06 microns are attainable with a 3 bar pump (5 W at 532 nm). Thelaser has a very high CW gain; e.g., if the gain in each fold is 10-20%,a total gain of about 7-8 can be achieved. Operation is CW or pulsed byadding an intracavity Q-switch, also represented by intracavity element34 in FIG. 1. Heat dissipation can be controlled by placing a heat sinkor other heat removal means 36, shown in FIG. 5, on the top and bottomface of block 12, if necessary. The high gain allows the use of a lowerabsorption laser material such as Nd:glass, which has the advantage thatthe absorption line is much broader than Nd:YAG so laser diode pumpsources without Peltier coolers can be used. These highly advantageousresults are obtained by the invention by achieving the seemlyimpossible, transverse longitudinal pumping-transverse to the laserblock and longitudinal to the laser resonator.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the scope of the invention whichis intended to be limited only by the scope of the appended claims.

What is claimed is:
 1. A mode matched diode pumped solid state laser,comprising:a block of laser material having a pair of opposed sides,adjustable cavity forming means positioned around the block to define alaser cavity having a tightly folded zig-zag resonator portion withinthe block between the opposed sides having vertices at an adjustablepreselected fold angle, a plurality of laser diode pumping sourcespositioned adjcent to at least one of the opposed sides andsubstantially aligned with the vertices of the zig-zag portion of theresonator the fold angle being steep, and selected to substantiallymatch the mode volume in the cavity with diverging pump radiation fromsaid laser diode pumping sources.
 2. The laser of claim 1 wherein thecavity forming means comprise a highly reflective mirror and a partiallytransmissive output coupler mirror, and a highly reflective coatingalong a portion of the opposed sides.
 3. The laser of claim 1 whereinthe laser diode pumping source is a laser diode bar containing aplurality of separate laser diode arrays.
 4. The laser of claim 1further including collimation means for collimating the output of saidlaser diode pumping sources.
 5. The laser of claim 4 wherein saidcollimating means is an optical fiber.
 6. The laser of claim 1 whereinthe mode volume is TEMOO.
 7. The laser of claim 1 wherein the lasermaterial is
 8. The laser of claim 1 further including a frequencydoubler positioned in the cavity.
 9. The laser of claim 1 furtherincluding a Q-switch positioned within the cavity.
 10. The laser ofclaim 1 further including precision spacing means for holding the fiberin a precise spaced relationship to the pump sources.
 11. The laser ofclaim 10 wherein the pumping sources is a laser diode bar of 1 cm lengthcontaining ten 1 W diode arrays, each 200 microns wide.
 12. The laser ofclaim 1 wherein the block is about 5 mm wide, the mode volume is about300 microns in diameter, and the fold angle is about 5°.
 13. A method ofefficiently pumping a solid state laser by means of a plurality of laserdiode pumping sources, comprising:forming a block of laser material withtwo opposed sides, forming a laser cavity having a tightly foldedzig-zag resonator portion within the block between the opposed sideshaving vertices at an adjustably steep preselected fold angle,positioning the pumping sources adjacent at least one of the opposedsides substantially aligned with the vertices of the zig-zag resonatorportion; selecting the fold angle to substantially match the mode volumewith diverging pump radiation from the pump sources.
 14. The method ofclaim 13 including forming the pump sources of a laser diode barcontaining a plurality of separate laser diodes.
 15. The method of claim13 including collimating the pump radiation by an optical fiber.
 16. Themethod of claim 13 including matching the pump radiation to the TEMOOmode volume.
 17. The method of claim 13 further including frequencydoubling the laser output.
 18. The method of claim 13 further includingQ-switching the laser.
 19. A collimated laser diode bar, comprising:alaser diode bar having a plurality of separate laser diodes spacedthereon; an optical fiber collimating means for collimating outputradiation from said laser diode; precision spacing means for holdingsaid collimating means in a precision spaced relationship to the diodebar with the diodes at its focus to assist in collimating the outputs ofthe diodes.
 20. The collimated laser diode bar of claim 19 wherein theprecision spacing means holds the fiber at a distance between about 20to 40 microns along the length of the diode bar.
 21. The collimatedlaser diode bar of claim 19 wherein the precision spacing means is amulti-step heat sink.
 22. A mode matched diode pumped solid state laser,comprising:a block of laser material having a pair of opposed sides,cavity forming means positioned around the block to portion within theblock between the opposed sides having vertices at a preselected foldangle, a plurality of laser diode pumping sources positioned adjacent toat least one of the opposed sides and substantially aligned with thevertices of the zig-zag portion of the resonator, means for preventingparasitic oscillations across said pair of opposed sides, the fold anglebeing steep, and selected to substantially match the mode volume in thecavity with diverging pump radiation from said laser diode pumpingsources.
 23. The mode matched diode pumped solid state laser of claim22, wherein said means for preventing said parasitic oscillationincludes said pair of opposed sides of said block of laser materialbeing non parallel to one another.
 24. The mode matched diode pumpedsolid state laser of claim 22, wherein said means for preventing saidparasitic oscillations includes areas of reduced reflectivity on thesurface of the one of said pair of opposed sides of said block of lasermaterial opposite to the side adjacent to said laser diode pumpingsources, said areas of reduced reflectivity disposed on regions of saidside directly across said block from each of said laser diode pumpingsources.
 25. The mode matched diode pumped solid state laser of claim 24wherein said areas of reduced reflectivity comprise an anti-reflectivecoating.